OBJECTIVES: The impact of nutrition status on outcomes in pediatric severe sepsis is unclear. We studied the association of nutrition status (expressed as body mass index z score) with outcomes in pediatric severe sepsis. DESIGN: Secondary analysis of the Sepsis Prevalence, Outcomes, and Therapies study. Patient characteristics, ICU interventions, and outcomes were compared across nutrition status categories (expressed as age- and sex-adjusted body mass index z scores using World Health Organization standards). Multivariable regression models were developed to determine adjusted differences in all-cause ICU mortality and ICU length of stay by nutrition status. SETTING: One-hundred twenty-eight PICUs across 26 countries. PATIENTS: Children less than 18 years with severe sepsis enrolled in the Sepsis Prevalence, Outcomes, and Therapies study (n = 567). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Nutrition status data were available for 417 patients. Severe undernutrition was seen in Europe (25%), Asia (20%), South Africa (17%), and South America (10%), with severe overnutrition seen in Australia/New Zealand (17%) and North America (14%). Severe undernutrition was independently associated with all-cause ICU mortality (adjusted odds ratio, 3.0; 95% CI, 1.2-7.7; p = 0.02), whereas severe overnutrition in survivors was independently associated with longer ICU length of stay (1.6 d; p = 0.01). CONCLUSIONS: There is considerable variation in nutrition status for children with severe sepsis treated across this selected network of PICUs from different geographic regions. Severe undernutrition was independently associated with higher all-cause ICU mortality in children with severe sepsis. Severe overnutrition was independently associated with greater ICU length of stay in childhood survivors of severe sepsis.